Two-way television and speech television



March 23, 1943.

s. B. WRIGHT TWO-WAY TELEVISION AND SPEECH TELEVISION Filed Aug. 24, 1940 4 Sheets-Sheet l //v VE/V TOR S. B. WRIGHT AT TORNEV March 23, 1943. s. B. WRIGHT TWO-WAY TELEVISION AND SPEECH TELEVISION 4 Sheis-Sheet 2 Filed Aug. 24, 1940 IN VEN TOP 5. B. WRIGHT I B Y ATTORNEY March 23, 1943. s. B. WRIGHT TWO-WAY TELEVISION AND SPEECH TELEVISION Filed Aug. 24, 1940 4 Sheets-Sheet 3'3 mmuaa l K uiotmxt INVENTOR S. B. WRIGHT ATTORNEK in IL 9 EN WL Qw Qw Ill.

Msw %low March 23, 1943. s. B. WRIGHT 2,314,471

TWO-WAY TELEVISION AND SPEECH TELEVISION Filed Aug. 24, 1940 4 Sheets-Sheet 4 TELEPHONE ATTORNEY Patented Mar. 23, 1943 TWO-WAY TELEVISION AND SPEEC TELEVISION Sumner B. Wright, South Orange, N. J., assignmto Bell Telephone Laboratories, Incorporated, New York, N. Y,, a corporation New York Application August 24, 1940, Serial No. 354,068 14 Claims. (01. lie-5.6)

This invention relates to signaling and particularly to a two-way television and speech transsired intervals, or (3) by signals from another source, speech signals for example.

In the communication system herein shown. and described for the purpose of illustration, there are provided two terminal stations, each equipped with television transmitting and receiving apparatus and with telephone transmitting and receiving apparatus connected by a transmission line including a repeating station. Television signals are transmitted over a' single transmission channel in opposite directions during non-concurrent time intervals. Speech signals are transmitted between the terminal stations over two additional transmission channels, one channel for transmitting in one direction and another channel for transmitting in the opposite direction. At one of the terminal stations there is provided a manual mulapparatus at the first terminal station. A third position of the manual switching means is provided for permittin the direction of transmission of the television signal to be reversed under control of speech signals generated at a terminal station and, when the manual switching means is in a fourth position, the direction of transmission of the television signals is automatically periodically reversed under control of a rotating commutator.

Figs. 2, 3, 4 and 5, when arranged side by side as indicated by the diagram of Fig. 1, constitute a diagrammatic view of a signaling system in accordance with the present invention.

Referring to the drawings, there is disclosed a signaling system comprising terminal stations A and B which are connected by a suitable transmission lineL. L, a coaxial conductor cable, for example, including a repeater station C.

At station A there is provided television scanning apparatus comprising a scanning disc l0 driven by a motor l4 and having apertures spirally arranged near the peripheral portion thereof for directing light from source ll upon elemental areas in succession of the subject I2, and a photoelectric cell l3 for receiving light reflected from the successively illuminated elemental areas. There is also provided the well-known cathode ray image producing apparatus 20 for producing under control 01" an image current received from station B, television images which may be viewed by the subject I2, the deflection of the cathode ray beam of the cathode ray tube 20 being controlled by the usual sweep control apparatus 2|. Synchronizing current from oscillator 25, which is here assumed to have a frequency of 6 kilocycles, is applied to a speed control circuit 26 for controlling the speed of motor M, as disclosed for example in U. S. Patent 1,999,376, granted to H. M. Stoller, April 30, 1935. Synchronizing current from oscillator 25 is also supplied to the cathode ray sweep circuits 2| for maintaining the image production in synchronism with the image scanning at station B. Current from a -kilocycle oscillator 22 is supplied to a harmonic producer 21. The harmonic producer 21 is connected to a band-pass filter 28 which selects a 2310-kilocycle current component to be impressed upon the modulator-demodulator 29, and is also connected to a band-pass filter 30 which selects a 2450-kilocycle current component to be impressed upon the modulator-demodulator 3| transmitted through equalizing network 3'! and through the armatures of relays 38 and 39 to the modulator-demodulator 29. Assuming that the television frequency band width is one megacycle, there will be produced in the modulator-demodulator 29 a modulated wave having a lower lit will be assumed for the present that all of side-band extending irom 1310 kilocycies to 2310 kilocycles which frequency band is passed through a band-pass filter 40 to the modulator-demodulator 3| where there will be produced a modulated wave the lower side-band of which extends from 140 kilocycles to 1140 kilocycles. The current having this frequency band is transmitted from modulator-demodulator 3I through the armatures oi relays 41 and 42, 1140 kilocycle lowpass filter 43, amplifier 44, equalizer 45, armatures of relays 46 and 41 and 140 kilocycle highpass filter 48 to the transmissionline L.

At station C, when the relays MI and 202 thereat are unactuated, as shown, the image cur- When the relays at station B are unactuated,

as shown, the image current coming from repeater station C is transmitted through 140 kilocycle high-pass filter I48 and through the armatures of relays I46 and I41 to the input of 1140 kilocycle low-pass filter I43. filter is connectedthrough the amplifier I44, equalizer I45 and the armatures ofrelays I38 and I33 to the input of modulator-demodulator I29, the output of which is connected through band-pass filter I40 to the input circuit of modulator-demodulator I3I. The output of modulator-demodulator I3I is connectedthrough the armatures of relays MI and I42, equalizer H5, 1000 kilocycle low-pass filter II 6 and amplifier I I1 to the image producing cathode ray tube I20 which produces an image of the subject I2 scanned at station A so that it may be viewed by the subject I I2 at station B.

At station A the 6-kllocycle synchronizing cur- The output of this rent from oscillator 25 and the '10-kilocycle cur- I rent from source 22 are impressed upon modulator 49 for producing a current having 64-kilocycle and 70-kilocycle components which are selected by the band-pass filter and transmitted over line L to repeater station C where the current is transmitted through a circuit comprising control circuit I26 for controlling the speed of driving motor II4 for scanning disc IIO so that the scanning of the subject H2 at station Bwill be maintained in synchronism with the image production by means of cathode ray tube 20 at station A. The 6-kilocycle synchronizing current from filter I53 is also impressed upon the-sweep circuits I2I for maintaining the image production at station B in synchronism with the scanning of the subject I 2 by means comprising scanning dis'c I0 at station A.

The 70 kilocycle component of the current produced by the demodulator I52 is selected by band-pass filter I54 and impressed upon the harmonic producer I21 for producing a current having 2450 kilocycle and 2310 kilocycle components. The 2450 kilocycle component selected by bandpass filter I30 is transmitted through armatures, I

of relays I34 and I35 and thro phase shifter I to the modulator-demodulator I23. This phase shifter may be adjusted to compensate for any 'difierence in phase which may exist between the received television signal impressed upon the modulator-demodulator I23 and the 2450- kilocycle current impressed upon the modulatordemodulator I23 from the filter I33 in order that the signal may be properly detected. The lower side-band of the 1310 kilocycle to the 23l0-kilocycle current from the output of modulatordemodulator123 is selected by band-pass filter I40 and impressed upon the modulator-demodulator I3I upon which is also impressed 2310- kilocycle current from band-pass filter I23 transmitted through a circuit including the armatures of relays I32 and I33. There is thus produced in the output of modulator-demodulator I3I an image current having a zero to 1000-kilocycle lower side-band which is transmitted through A, B and C are energized in the manner which will be explained below, the system is conditioned for transmitting-to station A the image current produced at station B as the result of scanning the subject II2 by the scanning apparatus comprisingscanning disc IIO, light source III and photoelectric cell H3. The television transmitting circuit of station B may be traced from photoelectric cell II3 through amplifier I33, equalizer I31, armatures of relays I33 and I33, modulator I29, band-pass filter I40, modulator I3I, armatures oi relays I and I42, low-pass filter I43, amplifier I44, equalizer I45, armatures of relays 'I46 and I41, high-pass filter I43 to line L. At repeater station 0 the line L is connected to the input of filter 233 through a circuit including the lower armature of relay 232. The image current from line L' is thus transmitted through filter 203, amplifier 234 and filter 205 to line L, the output of filter 235 being connected to the line L through a circuit including the lower armature of relay 23]. At station A the circuit may be traced from line L through filter 48, armatures of relays 46 and 41, low-pass filter 43, amplifier 44, equalizer 45, armatures of relays 38 and 33, modulator-demodulator 23, bandpass filter 40, modulator-demodulator 3|, armatures of relays H and 42, equalizer I5, lowpass filter I6 and amplifier I1 to the cathode ray tube 20 which produces an image 01' the subject For two-way telephone communication between the subscribers or subjects I2 and I12 there is provided a telephone subscribers set 53 which is connected to the hybrid coil 51 provided with a balancing network 58. From the hybrid coil 51 the speech transmission path extends through,

gain control potentiometer 53, amplifier 53, delay network 6|, modulator 62, supplied with 100-kilocycle carrier current from source 63, and -kilocycle to kilocycle band-pass filter 64 to line L. At repeater station C, the telephone current from station A is transmitted through band-pass filter 209, amplifier 2I0 and band-pass filter 2, At station B the spee'ch, current is transmitted through band-pass filter I35, gain control potentiometer I66 and amplifier I61 to hybrid coil 1, having a balancing network I53, and from the hybrid coil to the subscriber's set I53.'

Speech signals generated in the subscriber's set I56 at station B are transmitted through hybrid coil I51, gain control potentiometer I59, amplifier I60, l-kilocycle low-pass filter I64 to line L. At repeater station C the speech signalsare transmitted through low-pass filter 2I2, amplifier 2|3 and low-pass filter 2|4 to line L. At station A, the speech signals are transmitted through lowpass filter 65, transformer 68 and 69, gain control potentiometer 66; amplifier 61 and hybrid coil 51 to subscriber's set 56. The transformer 68 has two secondary windings and the transformer 69 has two primary windings. There is provided a relay through the armature of which the sec ondary windings of transformer 68 and the primary windings of transformer 69 are connected so as to establish two series-aiding circuits through the transformers when the relay 18 is unactuated, thereby permitting speech signal transmission through the circuit as described in U. S. Patent 1,749,851, granted to H. C. Silent, March 11, 1930. When the relay 18 is energized to open the circuit through this armature the windings are opposed to prevent speech signal transmission through the transformers.

The apparatus for controlling the direction of television transmission over the single channel provided for this purpose will now be described. There is provided a manually operated switch under control of the subscriber I2 at station A, this switch having an arm 1| which may be brought into engagement with a desired contact I, 2, 3, or 4 by turning the knob 12. When the switch arm 1| is brought into engagement with contact I, the direction of transmission between stations A and B is automatically reversed periodically at such a rate, for example, that at each station the successive image scanning periods, during each of which a complete image is produced, are separated by equal image scanning periods during which successive images are produced. at the other station. When the switch arm is in position 2, the system is in condition for television transmission continuously from station A to station B and, when the switch arm is in position 3, the system is conditioned for television transmission continuously from station B to station A. When the switch is in position 4 the direction of television transmission is reversed under control of speech currents. As shown in the drawing the camswitch 14 is operated when the switch arm H is on point I r 4 and released when it is on points 2 and 3.

It will be observed that there is no circuit connection to contact 2 of the manually operated switch so that, when the switch arm 1| is in position 2,'the switching relays at stations A, B and C are deenergized and the system is conditioned for transmission of television images from the control station A to the distant station B, as described above.

When the switch arm 1| is moved to contact 3.

grounded battery 12 is connected to the series circuit which may be traced from battery 12 through lead 1, relay 13, lead 8, contact of cam switch 14,

lead 6 and through relays 41, 46, 4|, 42, 35, 34, 32, 33, 39 and 38, in order, to ground. The operation of relay 13 completes a circuit through the relay armature for transmitting 20-kilocycle current from oscillator through band-pass filter 16 to line L. At station C the -kilocycle current is transmitted through band-pass filter 2|5 and amplifier 2|6 to detector 2" for supplying operating current to the windings of switch relays 2M and 282. The 2|l-kilocycle current is also transmitted from the output of amplifier 2"}, through band-pass filter 2|8 to line L. At sta tion B the 2'0-kilocycle current from line L is transmitted through band-pass filter I16 to detector I15 for supplying energizing current to the relays connected in the series circuit which. may be traced from grounded battery through the output of detector I15, and through relays I38, I39. I33, I32, I34, I35, I42, |4|, I46 and I41, in order. to ground. When these various switching relays at stations A, B and C are operated the system is conditioned for television image transmission from station B to station A, as described above.

When the switch arm H is brought into position I, grounded battery 11 is intermittently connected, through the conducting segments of commutator 18, to the series circuit which may be traced through lead 5, switch contact I, switch arm 1|, lead 1, relay 13, lead 3 and cam switch 14, to ground at 88, to cause the intermittent operation of relay 13 and, as a result, the transmission of current from oscillator 15 to stations C and B for causing the intermittent operation of the switching relays thereat. Another circuit which iscompleted when the switch arm 1| is in position I may be traced from grounded battery 11 through commutator 18, lead 5, switch arm 1|,.resistor 19 and condenser 88 to ground and. in shunt with the condenser 88, through resistor 8|, lead 6 and relays 41, 46, 4|, 42, 35, 34, 32, 33, 39 and 38, in order, to ground. The commutator 18 is driven by motor 82, the speed of which is maintained constant by current from oscillator 22 supplied to the speed control circuit 83 as described in the Stoller patent, supra. The artificial line comprising resistors 19 and 8|, and condenser 86 delays the operation of relays 41,

46, 4|, 42, 35, 34, 32, 33, 39 and 38 at station A to compensate for the delay in transmission over line L to station B and, if desired, a similar network may be employed at station C for delaying the operation of relays 2M and 282 to compensate for the transmission delay over line L going from station C to B. Thus the relays at stations A, B and C for reversing the direction of transmission may be switched substantially simultaneously during an interval commencing subsequent to the completion of a single scanning of the field of view at station A and prior to the commencement of scanning of the field of view at station B. Thus, after the subject I2 at station A has been scanned for a period of second, for example, and after the image current has been transmitted over line L, L' to control the image production at station B, the switching relays are operated to condition the television transmission channel for transmitting the image current, generated at station B as a result of scanning subject I I2, to station A for controlling the production of an image at that station.

When the switch arm 1| is moved to contact 4, the system is conditioned for television transmission from station A to station B when neither subscriber is talking into the transmitter of the subscriber's set or when subscriber i2 is talking.

Thus, under these conditions, the subscriber H2 at station B can see an image of the subscriber I2. However, when the subscriber I2 talks into the transmitter of subscribers set 56 the television channel is switched or conditioned for transmitting an image of the subscriber H2 at station B to station A, thus enabling the subscriber I2 to see an image of subscriber 2. To cause the energization of the switching relays. the speech current generated in the subscriber's set 56 is transmitted through hybrid coil 51 and amplifier 60 to the delay circuit 6|, which stores the speech energy, while a portion of the speech current of which flows through the windings of relays Ill, 85, and 85 in series to cause these relays to operate. It should be noted at this point that, when speech current is being received at station A through the circuit including transformers 68 and 69, a portion of the speech energy is diverted to the circuit including detector 89 and relay 9!). The relay 90 when thus energized opens the series circuit including the windings of relays I0, 85 and 86 to prevent their energization. The operation of relay 85 will open the short circuit across the output of delay network 6! to permit the speech current to be transmitted over the circuit to modulator 62 and the operation of relay 10 will prevent the transmission of speech current through transformers 68 and 68, as explained above, thus preventing echoes from being received at station A. The operation of relay 86 will complete a circuit from grounded battery 81, through the relay armature, lead 9, contact 4, and switch arm 1|, lead I, relay I3, lead 8 and through a contact of switch 14 to ground at 88. Another circuit which is completed when the switch arm II is in position 4 may be traced from grounded battery 81 through the armature of relay 86, lead 9, contact 4, switch arm Ii, resistor 19, condenser 88 to ground and, in shunt with condenser 80, through resistor 8|, lead 8 and relays 41, 46, 4|, 42, 35, 34, 32, 33, 39 and 38, in order, to ground. Due to the operation of relay 13, current is thus transmitted from oscillator 15 to stations C and B for controlling the operation of switching relays thereat, and the switching relays at station A are directly energized by current from battery 81 to condition the television channel for transmission from station B to station A.

In the system as specifically shown and described herein. when the television channel is under control of the speech waves, the direction of transmission of the television signals is opposite to the direction in which the speech waves are being transmitted. With this arrangement, the subscriber who starts speaking first can see an image of the subscriber to whom he istalking and, when that subscriber stops talking and the second subscriber starts talking the direction of television transmission is reversed and the second subscriber can see an image of the first subscriber. If desired, of course, the system may be arranged to transmit an image of the subscriber who is speaking to the listening subscriber. Moreover, if desired, station B as well as station A, may be provided with speech that shown at station A, and the control circuit including detector I15 omitted from station B,

' so that the direction of television transmission can be switched under control of speech current produced at either station A or station B. In this case, the stations A and B normally would be conditioned for transmitting television signals and, if the subscriber H2 at station B, for examterminal equipment, like A current is diverted into detector 84, the output ple, were speaking, the television circuit at station B would be switched to the receiving condition so that the subscriber at station B would be able to see an image of the subscriber l2.

What is claimed is:

1. A combined television and' sound system comprising stations connected by a plurality of communication channels, means for transmitting sound signals over one of said channels, and

means associated with said one channel and controlled by said sound signals, for controlling another of said channels for the transmission thereover of television signals.

2. A combined television and sound system comprising stations connected by a plurality of communication channels, means for transmitting sound signals over one of said channels, means for transmitting television signals in either direction over another of said channels, and means controlled by said sound signals for determining the direction of transmission of said television signals over said other channel.

3. A combined television and telephone system comprising a plurality of terminal stations, television transmitting and receiving apparatus and telephone transmitting and receiving apparatus at each of said stations, a television transmission channel connecting said stations, switching means at each of said stations for connecting the television transmitting apparatus and the television receiving apparatusv to said transmission channel alternatively, and means under control of the telephone signals produced at one of said terminal stations for controlling said switching means at at least one of said terminal stations.

4. A combined television and telephone system comprising two terminal stations, television transmitting and receiving apparatus and telephone transmitting and receiving apparatus at each of said stations, a television transmission channel connecting said stations, switching means at each of said stations for connecting the television transmitting apparatus and the television receiving apparatus to said transmission channel alternatively, and means under control of the telephone signals produced at one of said terminal stations for controlling said switching means at both of sad terminal stations.

5. A combined television and telephone system comprising two terminal stations, television transmitting and receiving apparatus and telephone transmitting and receiving apparatus at each of said terminal stations, a transmission channel including a repeater station for connecting the terminal stations, switching means at each of said stations for conditioning the system for television transmission from either terminal station to the other terminal station alternatively, and means undercontrol of said telephone signals for controlling said switching means at each of said stations.

6. A combined television and telephone system comprising two terminal stations, television transmitting and receiving apparatus and telephone transmitting and receiving apparatus at' each of said terminal stations, a transmission channel including a repeater station for connecting the terminal stations, switching means at each of said stations for conditioning the system for television transmission from either terminal station to the other terminal station alternatively, and means for preventing the control of said switching means by telephone signals produced at one of said terminal stations while telephone signals are being transmitted from the other terminal station to the telephone receiving apparatus at the first terminal station.

7 In a carrier current signaling system including a plurality of terminal stations, signal generating means and signal reproducing means at one of said terminal stations, carrier current modulating-demodulating means at said station, and switching means for impressing signals produced by said signal generating means upon said modulating-demodulating means to produce a signal modulated carrier current and for transmitting the signal modulated carrier current or, alternatively, for impressing a received signal modulated carrier current upon said modulating-demodulating means to produce a demodulated Signaling current and for impressing said demodu-v lated signaling current upon said signal reproducing means.

8. A two-way carrier television system including a plurality of terminal stations, television transmitting and receiving apparatus at each of said stations, carrier current modulating-demodulating means at each of said stations, carrier current transmission means connecting said stations, switching means for connecting the television transmitting apparatus and the transmission means to the modulating-demodulating means at one of said stations and for connecting the transmission means and the television receiving apparatus to the modulating-demodulating means at the other of said stations or, alternatively, for connecting the television receiving apparatus and the transmission means to the modulating-demodulating means at said one station and for connecting the television transmitting apparatus and the transmission means to the modulating-demodulating means at said other station.

9. A carrier current system in accordance with claim 7 in which there is provided a second signal generating means for controlling said switching means.

10. A two-way carrier television system in ac cordance with claim 8 in which there is provided means for actuating said switching means at regularly spaced time intervals.

11. In a carrier current signaling system, a first and a second modulator-demodulator, a first and a second source of carrier current of difierent frequency, respectively, and switching means for connecting the first source of carrier current to the first modulator-demodulator and the second source of carrier current to-the second modulator-demodulator or, alternatively, for connecting the second source of carrier current to the first modulator-demodulator, and the first source of carrier current to the second modulator-demodulator.

12. In a carrier current signaling system a first and a second modulatordemodulator, means for connecting the output of the first modulator-demodulator to the input of the second modulatordemodulator, a first and a second source of carrier current of different frequency, respectively, asource of signals, a signal reproducing means,

ing means is in a certain condition or, alternatively, for connecting the second source of car'- rier current and the transmission Path to the first modulator-demodulator and for connecting the first source of carrier current and the signal reproducing means to thesecond modulator-demodulator when the switching means is in a different condition, and means for energizing said switching means for changing the condition thereof.

13. In a carrier signaling system, a first modulator-demodulator, a second modulator-demodulator, a first source and a second source of carrier current, the frequency of the first source a transmission path, switching means for con-' carrier current and the transmission path to the second modulator-demodulator when the switchbeing lower than that of the second source, a source of signals, a transmission path, signal reproducing means, a first switching means for connecting said source of signals to said first modulator demodulator, a second switching means for connecting said first source of carrier current. to said first modulator-demodulator, thereby producing a modulated carrier signaling current, means for selecting one side-band of the modulated current produced in said first modu lator-demodulator and impressing it upon said second modulator-demodulator, a third switching means for connecting said second source of carrier current to said second modulator-demodulator a fourth switching means for connecting said second modulator-demodulator to said transmission path, said transmission path including means for selecting one side-band of the modulated current produced in said second modulatordemodulator, and means for operating all of said switching means simultaneously for disconnecting the circuits previously connected by said switching means and for connecting the transmission path to said first modulator-demodulator through said first switching means, for connecting said second source of carrier current to said first modulator-demodulator through said third switching means, for connecting said first source of carrier current to said second modulator-demodulator through said second switching means, and for connecting said signal reproducing means to said second modulator-demodulator through said fourth switching means, thereby demodulating a modulated carrier current received over said transmission path and impressing it upon said signal reproducing means.

14. A television system comprising a plurality of terminal stations each having terminal television transmitting and receiving apparatus, a transmission channel connecting said terminal stations, switching means for reversing the direction of television image transmission between the terminal apparatus at said terminal stations, a plurality of means for controlling the operation of said switching means and manually operable means for selecting said controlling means alternatively.

SUMNER B. WRIGHT. 

